This invention relates in general to telephony and in particular to the art of using the Signaling System Number 7 (SS7) protocol to effect a database lookup by a Service Control Point (SCP) to assist in routing a toll call in a telephone network.
The conventional telephone network, known as the Public Switched Telephone Network (PSTN), may be thought of as at least two different networks. The first of these networks is called an End Office (EO), and is typically operated by Local Exchange Companies (LEC), and the second-the network that carries toll trafficxe2x80x94is typically operated by an Inter-Exchange Carrier (IXC). These distinctions are used only for illustrative purposes. It may be the case, for example, that the same company serves as both the EO and the IXC. Additionally, the EO could be a wireline telephone company or a wireless telephone company, providing a subscriber loop via networks called Wireless Local Loops.
To complete a call that originates at an EO, a gateway switch functioning as an originating toll station (OTS) or a tandem toll office (TO) is typically accessed. The OTS and the TO are ordinarily controlled by the IXC. Once the gateway switch takes control of the telephone call, the call can be completed without accessing the EO, which originated the call. In such a network, edge switches are used to concentrate customer traffic from EOs and feed it to a carrier network.
Other configurations of network interconnections are also possible. For example, a direct link to a carrier of toll traffic, such as an IXC or other carrier, can be established between a Customer Premise Equipment (CPE) located at a customer site and the gateway switch. In such cases, the IXC traffic that originates at the customer site is concentrated or xe2x80x9caggregatedxe2x80x9d by the CPE and routed via the toll carrier""s trunks. These CPE vehicles that perform such traffic aggregation or gateway function between a customer site and the carrier network are also called edge switches.
An edge switch is a switch located at the edge of a network, typically the EO network or a CPE, where traffic from network nodes such as the EOs or CPEs crosses over to the toll or other carrier networks. The edge switch network configuration can be considered as a network comprising several subtending nodes causing the traffic to converge at a concentrator node. Thus, in a PSTN, the EO or the CPEs form the subtending nodes and the IXC toll tandem switches or other carrier vehicles act as concentrator nodes or gateways to the longdistance trunks. Thus, the subtending nodes or edges may be operated by one entity such as a LEC or a large customer such as a major bank or a government agency, whereas the concentrator or gateway may be operated by an IXC or a toll carrier or other entity. In other configurations, the edge switch vehicles could be operated by the toll carriers and the CPEs or the nodes that feed the traffic to the edge switches could be operated by the so-called nodal customers, such as large banks, or government agencies.
In the following discussion, reference is made to an xe2x80x9cedge switch.xe2x80x9d This reference should be understood to encompass all configurations of switching systems that could serve the purpose of establishing an interconnection between two switching networks, including, but not limited to, an EO switching system or a switching system such as a Private Branch Exchange (PBX) or other switch serving as a CPE. An example of an edge switching system is a class 5 system such as the Lucent(copyright) 5ESS(trademark) switching system. The 5ESS(trademark) is described by K. E. Martersteck, et al., in ATandT Technical Journal, Volume 64, No. 6, part 2, pp. 1305-1564 (July/August, 1985). Other examples of switching systems that could function as edge switches are the DMS-250(trademark) switching system marketed by Nortel, Inc.; the EWSD(trademark) switching system marketed by Siemens AG of Munich, Germany; the Lucent(copyright) DEFINITY(trademark) PABX system; and the NEAX-51E(trademark) switching system marketed by Nippon Electric Corporation of Japan.
Similarly, a reference in the following discussion to a xe2x80x9ctoll tandemxe2x80x9d should be understood as encompassing any toll switching system or other similar vehicle that can determine the routing by either looking up from a traditional database or by interfacing with an intelligent network database such as a Service Control Point (SCP). The toll tandem switch may be, illustratively, an electronic program-controlled telephone switching system of the No. 4ESS(trademark) design as described by A. E. Ritchie, et al., in the Bell System Technical Journal (BSTJ), Volume 56, No. 7 (September, 1977). The 4ESS(trademark) switch performs multiple functions: as an originating switch, and as a toll tandem, and as a gateway to the SCP database. When it functions as an originating switch, the 4ESS(trademark) switch is programmed to open a voice connection to a subscriber to play announcements, and receive input as touch-tone(trademark) digits or other forms prior to routing a call on a network trunk. Thus, an originating switch such as a 4ESS(trademark) is capable of engaging in a dialog with a subscriber to obtain additional information (e.g., authorization code for special calls).
A telephony Advanced Intelligent Network (AIN) comprises a network within the PSTN comprising switching systems such as the edge switches and the toll tandem switches, adjunct computer processors and other communicating components equipped with the capability to communicate using an out-of-band signaling method known as Common Channel Signaling (CCS). CCS is a high speed data link configured to carry network control information to and from various elements of the network. The AIN is described in detail in U.S. Pat. No. 5,247,571, which is incorporated herein by reference. For more information on intelligent telephony networks, see The Intelligent Network Standards: Their Application to Services (Igor Faynberg, Ed.), McGraw Hill Series on Telecommunications (November 1996).
The details of the usage of CCS to control and manage a telecommunications network are given in U.S. Pat. Nos. 5,515,427 and 4,277,649, both of which are incorporated herein by reference. An example of the CCS signaling method is CCS No. 7 which is also known as Signaling System 7, or SS7. SS7 is the name given to a suite of layered communication protocols that are used to access telephony databases, to establish and maintain telephone calls, and for other purposes. The part of the SS7 signaling protocol that is typically used by an AIN-equipped switching system to access telephony databases to obtain special instructions is called the Transaction Capabilities Application Part (TCAP).
U.S. Pat. No. 5,901,213, by Benhabib, et al., whose contents are also incorporated by reference, describes a virtual dedicated access by telecommunication subscribers to an IXC provided by way of an intelligent local EO that routes calls either to the IXC or to a local EO. The intelligent local EO itself advantageously performs inter-exchange processing of calls, as required, for calls that originate with, or terminate at, a customer rather than automatically route calls to the IXC for such inter-exchange processing, as was previously required.
In general, in an AIN, a switching system is equipped with at least one triggering device implemented as software, circuitry, or a combination of the two. The triggering device is configured to recognize the occurrence of certain types of phone calls (xe2x80x9ctrigger conditionsxe2x80x9d) and respond accordingly by handling such calls in a special way. Typically, to provide special handling in response to a trigger condition, the switching system suspends normal execution of the phone call, communicates with another network element to obtain special instructions, and handles that phone call according to the special instructions. In contrast, ordinary telephone calls do not require any special handling and therefore do not require special instructions from other network elements. Rather, in processing ordinary calls, local and toll tandem office switches function in a normal way and route such calls according to the traditional telephony methods.
Several types of trigger conditions may be specified in an AIN-equipped switching system. These include Originating Trigger conditions, Mid-Call Trigger conditions and Termination Trigger conditions, depending on whether the special handling of the call is performed based on a triggering event at the time of initiation of a call, during the course of a call, or at the time of termination of a call. An example of an originating trigger condition is an 800-call. This trigger condition is also called a Dialed Number trigger condition (DN trigger). Here, the special handling of the call is triggered by a user dialing the 800-number. In general, such numbers are translated to regular telephone numbers called Plain Old Telephone Service (POTS) numbers before they are routed to proper destination points via the traditional methods. Handling an 800-number call within an AIN network is described in detail in U.S. Pat. No. 5,425,090, which is incorporated herein by reference. Other examples of trigger conditions are the Off-hook Immediate trigger condition (OHI) and the Off-hook Delay trigger condition (OHD).
A switching system that is provisioned with a class of pre-defined trigger conditions and equipped to communicate with the telephone network via CCS is called an AIN-equipped switching system. In the description given herein, the toll tandem office switching system is assumed to be equipped with AIN call triggering capabilities such as those described in the Bellcore Advanced Intelligent Network (AIN) 0.1 Switching Systems Generic Requirements (TR-NWT-001284).
A Service Control Point (SCP) is a part of an intelligent telephone network that provides a switching system with certain routing related information stored in a database coupled to it. For example, a SCP may store the Inward Wide-Area Telecommunication Service (INWATS) database, which translates a 10-digit 800-number to a POTS number. An example of an SCP is the 2NCP(trademark) (xe2x80x9cnetwork control pointxe2x80x9d) system commercially available from Lucent Technologies, Inc.
The SCP also supports the deployment of a variety of other telephone services such as the Software Defined Network (SDN) service, commonly known as the Virtual Private Network (VPN) service. SDN allows a subscriber who desires services at geographically distant locations to define a private network within the PSTN. The SDN could be viewed as a network within a network, defined entirely by software. Each subscriber is given a 7-digit telephone network, which is translated to a 10-digit POTS number by the SCP. In an intelligent telephone network, the SDN service is capable of offering a variety of customized intelligent call processing services tailored to a calling party or a calling station.
For the purposes of describing this invention, two types of telephone calls are assumed. A telephone call of the first kind is defined as one that requires additional information from a toll subscriber. Though the subscriber may be physically connected to a nodal switch such as a PBX functioning as a CPE that is in turn connected to an edge switching system as the entry point to the toll carrier""s network, for toll calls he or she is assumed to be a subscriber of the toll carrier. Suppose the toll subscriber makes a telephone call. This call could be a local call or it could be a toll call. This discrimination can be made by performing a lookup in a database such as the 2NCP(trademark) database. When it is determined that the toll subscriber made a toll call that requires additional informationxe2x80x94such as an authorization code or a credit card numberxe2x80x94which can be obtained in the form of an interactive dialog, the toll call is further processed by establishing a voice path between a suitably equipped and programmed toll tandem office and the subscriber. At the same time, control of the call is transferred to the toll tandem office to handle the call from that point.
All other calls are termed as calls of the second kind. For example, a simple number translation without the need for additional user input, such as an 800-number call, is defined as a call of the second kind. Once this is determined, the edge switch can perform the appropriate routing decision without any further information from the subscriber. Some other calls that arrive at an edge switch may be local to the network served by that switch, with no need to access the toll tandem. This may happen where the edge switch is a class 5 switch serving a metropolitan area.
When a toll telephone call originates at a toll subscriber""s telephone connected to a PSTN or a CPE connected to a CPE network, the PSTN or the CPE network presents the call to the edge switching system. As the toll subscriber dials the digits corresponding to a telephone number of a destination station (called party number), they are captured by special circuits located in the edge switch. It should be noted that though the traditional language xe2x80x9ccircuitxe2x80x9d is used to describe the various components of the switching systems or of other elements of the telecommunication networks, the invention encompasses computer executable software code normally resident on a computer readable medium which, in combination with a computer or the like, performs the function of these xe2x80x9ccircuitsxe2x80x9d as well. Accordingly, this invention should be understood to contemplate a complete equivalence between an electronic circuit and a programmed general purpose computer comprising a microprocessor executing software code configured to perform the principles of the invention.
When the toll subscriber dials a toll number in prior art systems, the call is transferred by the edge switch to the toll tandem. This is done by opening a voice path between the edge switch and the toll tandem and transferring control of the call to the toll tandem. If the AIN is not provisioned to treat the call as a trigger condition, i.e., the phone call does not cause an AIN trigger condition, the call is completed by the toll tandem in the traditional way. If, on the other hand, a trigger condition is provisioned in the toll tandem switch for the call, the toll tandem switch queries the 2NCP(trademark) database for special routing or billing instructions and receives any such instructions needed to complete the call. Based on these instructions, the toll tandem may determine that the call does not need any further input from the toll subscriber. In such cases, the call is routed in the traditional way. If, on the other hand, the instructions from the 2NCP(trademark) database specify that additional input is required from the toll subscriber, the toll tandem enters into an interactive dialog with the toll subscriber, plays appropriate signals such as voice prompting messages, and receives the input from the toll subscriber.
It should be noted that when an additional input is required from the toll subscriber, the edge switch opens a voice path and transfers the control of the toll call to the toll tandem in order to reach the 2NCP(trademark) database. This process of delivering a call to a toll tandem node in order to reach the 2NCP(trademark) database is called chaining the query (or chaining the call) through the toll tandem. In trying to accommodate the chaining of calls to provide an access gateway to the 2NCP(trademark) database, processing capacity of the gateway is consumed in processing calls that could have been routed without accessing the toll tandem in that way.
Using a toll tandem such as a 4ESS(trademark) to make the routing decisions for calls that can be handled by the edge switches wastes the resources of the toll tandem, which can be put to better use in providing interactive dialog for calls requiring more sophisticated routing as described above. If a direct CCS connection were provided between the edge switches and the 2NCP(trademark) database, only certain types of calls would be handled by the 4ESS(trademark) toll tandem, thereby conserving its processing capacity for other purposes.
In cases where the edge switches are operated by entities different from the ones operating the concentrator node, there is an additional problem. Though SS7 is a xe2x80x9cstandardxe2x80x9d way of accessing the SCP database, the particular implementation or configuration of the protocol may be different among the various edge switch vendors. In such a case, in order to communicate with a 4ESS(trademark) toll tandem, a edge switch vendor must conform to the 4ESS(trademark) implementation of the SS7 protocol. Thus, the operator of the edge switches will have only a limited number of vendors from whom to select the edge switches that can communicate with the 4ESS(trademark) toll tandem. If there exists a direct connection between a edge switch and the SCP, a multi-vendor network can be built.
Currently, the protocols used to interface with the 2NCP(trademark) database are defined as non-standard or proprietary methods. This situation could be improved by allowing an open network interface to a hitherto proprietary network interface to connect to the 2NCP(trademark) database. This serves the purpose of allowing devices from several different vendors to communicate with the 2NCP(trademark) database using their own proprietary methods. Additionally, this preserves the existing customer logic intact.
There is a need, therefore, for a method and system to enable direct access to the 2NCP(trademark) database for an edge switch to determine if a call requires additional information from the subscriber, without the 4ESS(trademark) toll tandem acting as a gateway to the SCP. There is also a need for improvement over the prior art to provide a network interface as a way to allow access to the 2NCP(trademark) database while maintaining transparency to the customers such as the nodal operators.
The above-identified problems are solved and a technical advance is achieved in the art by providing a method and system for an edge switch to access a Service Control Point (SCP) to make a preliminary determination of the call. In one aspect, the present invention is a system wherein a first switch having a class 5 design is connected via a first common channel signaling link to an SCP either directly or via a Segmentation Directory. The first switch is also connected to a second switch, preferably a class 4 office, via a voice path and optionally via a second common channel signaling link. The second switch is in turn connected to the SCP either directly or via a third common channel signaling link. The first switch is assumed to be AIN-equipped. When the first switch receives a call from a calling party, it formulates and transmits a query message to the SCP and receives a response message. Based on the information contained in the response message, the first switch completes the call or delivers the call to the second switch in order to query the database again and determine what additional information should be collected from the calling party.
In another aspect, the invention is a method for obtaining capacity relief by reducing call volume (load) at the second switch whereby the first switch receives call discrimination information by querying an SCP and routes the call via alternate paths if the call does not require the establishment of a voice path between the first switch and the second switch.
By configuring components of a telecommunications network in a manner exemplified by a preferred embodiment described below, the present invention (i) provides a method of obtaining capacity relief for certain other components of the network; (ii) provides a method of customizing an existing nodal database capable of providing proprietary services to provide similar or same services over a different interface, preferably an industry standard interface, thereby providing interface transparency to existing customers while facilitating the reuse of network components for new customers; (iii) provides an industry standard way to connect to an IXC vendor""s nodal services, enabling such services to be expanded to a multi-vendor switching base; (iv) provides a network framework that allows service or customer specific information presently derived from nodal trunks or switches to be defined and controlled in SCP databases, and permits future extensions to switched access traffic on edge vehicles; and (v) creates an infrastructure that permits an early determination to be made regarding the appropriate sub-network that is best able to process a call, based on a need for a specific type and number of resource(s).